Recently, semiconductor devices such as IC and LSI have been widely used in electronic equipments or electric equipments for miniaturization of the devices and for giving multifunctions to the devices. However, the use of the semiconductor devices causes decrease in resistance of the electronic equipments and electric equipments against anomalous high voltage such as noise, pulse or static electricity.
In order to ensure the resistance of electronic equipments and electric equipments against anomalous high voltage such as noise, pulse or static electricity, film capacitors, electrolytic capacitors, semiconductor ceramic capacitors, laminated ceramic capacitors are used. These have excellent characteristics for absorption and control of noises of relatively low voltage or high-frequency noises, but they exhibit no effect on pulses or static electricity of high voltage and sometimes cause wrong operation or rupture of semiconductor devices.
In order to absorb and control pulses or static electricity of high voltage, SiC and ZnO type varistors are used. However, these have no effect for absorption and control of noises of relatively low voltage and high-frequency noises and are apt to bring about wrong operation.
Under the circumstances, SrTiO.sub.3 type varistors have been developed to be effective against noises of relatively low voltage or high-frequency noises and pulses or static electricity of high voltage.
However, owing to the high impedance of elements, the SrTiO.sub.3 type varistors also have the problems that they are low in the effects to absorb and control pulses of relatively low voltage or high-frequency noises applied to signal lines.
The inventors have noticed that the high impedance is caused by a barrier formed at electrode part. Accordingly, the object of the present invention is to attain the high effects to absorb and control pulses of relatively low voltage and high-frequency noises applied to signal lines by reducing the impedance by destroying the barrier formed at the electrode part.